Branded as ‘the sport of fitness’, CrossFit is a burgeoning exercise regime that has surpassed the growth of well-known fitness franchises. In addition to its comprehensive fitness regime, it claims to offer a supportive community, which aims to ensure that people do not exercise ‘together alone’. The tight-knit – almost insular – nature of this community, as well as some of its more extreme practices, have led followers and detractors alike to characterise CrossFit as a cult. This article argues that the ‘cult’ label is too parochial and, instead, applies Susie Scott’s notion of ‘reinventive institutions’ to explain why CrossFit is so polarising. With its emphasis on voluntarism, performative regulation and mutual surveillance, the concept of the ‘reinventive institution’ offers a more useful and expansive theoretical tool that allows us to understand how power, identity construction and self-transformation operate in CrossFit.